If you want to stand firm in a negotiation, put down that hot cup of coffee.

While we love coffee — worldwide, we drink 500 billion cups a year — holding a hot beverage has strange effects on our willingness to accommodate the person we're talking to.

A 2008 study by Lawrence Williams of the University of Colorado and John A. Bargh of Yale sheds light on why.

Researchers asked participants to come to the lab to answer a short questionnaire — standard research practice, right? But the experiment started before they entered the room.

Each participant was joined by a research assistant while taking the elevator up. The assistant had her hands full; at one point, she asked the participant to hold a cup of coffee while she wrote his or her name down.

Half the participants held a hot cup of coffee, and the other half held an iced coffee.

When the participants got to the lab, they were asked to rate a stranger's personality — whether they were generous, caring, good-natured, or otherwise warm.

The results: The participants who held the warm coffee said that the individual had a warmer personality. The authors concluded that holding a warm object leads people to regard others more fondly.

According to Tel Aviv University professor Thalma Lobel, this is part ofembodied cognition, a growing field within psychology that shows how your mental life is a part of your physical life. She writes about it in her new book "Sensation: The New Science of Physical Intelligence."

"As children, we first learn the concrete concepts of close or far, smooth or rough, warm or cold," Lobel says. "On the basis of these concrete concepts we learn more abstract concepts. When we touch something warm, without our being aware of that process, it activates the concept of a warm personality."

Another experiment by Williams and Bargh helps us see how a hot beverage can derail your negotiations.

In this experiment, they told participants they were going to review a new product — a therapeutic pad — as part of a consumer marketing study. The pad was either hot or cold; participants held it for a moment before deciding whether to tell friends to buy the same pad.

But then the real experiment started: Researchers asked participants to select a reward for being a part of the study. As Lobel reports, participants could either enjoy a refreshment for themselves or give a gift certificate to a friend. Only 25% percent of the people who held the cold pad chose the gift, while about 50% of the people who held the hot pad picked it.